The present invention relates to a method for permanently joining at least essentially flat support materials on substrates, in particular, for laminating plastic films onto metal substrates, and also to the products or composite materials produced in this way, in particular, metal substrates laminated with plastic film, and also to its use.
Various methods are known for the coating of metal substrates, especially plate-shaped metal substrates, with a printing or coating material visually and/or tactilely changing one or both sides of these substrates.
For example, in the field of producing coated or printed metal plates or metal sheets, coatings and printing inks are used that react to UV or which contain solvents. In particular, producers of, e.g., metal packages or screw plugs for jars and bottles, crown caps, technical cans, food or aerosol cans, and the like, as well as producers of a plurality of other products made from coated and printed metal (e.g., toys, decorations) are increasingly confronted with questions and problems, primarily in the fields of environmentally friendly solvents and food compatibility.
Color and/or printed metal products according to the current state of the art are predominantly produced with extremely high energy and investment-associated expenses and also with high environmental risks:
In a first work step, one side of the metal plate is coated with a base coating for later printing, with solvent coatings being dried thermally by means of technically very complicated, large-volume, and high-investment drying furnaces for metal plates transported in a nearly vertical arrangement. Equally, the so-called protective coating for the other plate side is applied in a second separate, but equally complicated work step. In turn, in a third separate, equally complicated work step, the one-sided printing of the metal plates is then performed, in turn, with subsequent complicated thermal drying. A protective or high-gloss coating on the printing inks is completed in another, separate, fourth work step with comparatively high expense like for the base coating.
In the use of UV-reactive coatings and inks, identical production steps are necessary, with merely the drying of these coatings and printing inks not being performed thermally, but instead by UV irradiation of the metal plates, which is similarly very expensive in terms of energy and requires high investment.
The emission of volatile organic compounds is an increasingly important problem for metal coatings particularly in the processing of solvent-containing coatings and printing inks. In addition, coating and printing methods used today command extremely high costs for investment, space, energy, and operation, as well as for meeting the increasingly production-restrictive legal emission regulations.
Producers of coated and/or printed metal products predominantly process metal plates according to the methods described above in widths or thicknesses of 0.05 to 1.0 mm and in many different dimensions of, in general, at least 200×200 mm—according to the end products to be produced. The end products are produced, for example, by means of stamping blanks from a coated and/or printed metal plate and then shaping these blanks according to the end product.
In addition, various methods for laminating metal surfaces are known from the state of the art.
For example, from DE 100 04 593 C1 a special method for producing blanks for motor vehicle license plates, wherein a fed sheet band with printed film is laminated by expanding the film printed undersized to a controllable laminate distance before and/or during the lamination. The method described there is suitable only for the special problem of producing blanks for motor vehicle license plates, but in general is not suitable for laminating arbitrary support materials on arbitrary substrates and thus is not usable universally.
DE 44 20 532 A1 describes a method for producing a metal can, a device for performing this method, and also the metal can produced according to this method. In the method described in DE 44 20 532 A1, a plastic film blank produced from a special plastic film is laminated onto a completed can body. This is relatively complicated and only slightly flexible in terms of application.
DE 692 19 041 T2 describes a device for laminating can blanks, wherein the bonding of thermoplastic films on a metal band is noted with reference to JP 63203324A.
Finally, from the state of the art, other plastic materials, especially films of a wide variety, are known, which have a thermal adhesive construction and in this way are suitable for lamination, preferably on metal bands. For example, DE 101 30 005 A1 describes a method for coating the surface of a metal band with a plastic film, wherein a special plastic film with thermal-adhesive properties is laminated onto the metal band such that the metal band is heated to a certain temperature exceeding the melting temperature of the plastic film to be laminated, in order to be able to be connected to the metal band. The method described there is limited to special plastic materials and consequently is not usable universally.